Title

Author

Date of Award

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Mechanical Engineering

First Committee Member

Andrew T. Hsu, Committee Chair

Second Committee Member

Ned H. C. Hwang, Committee Member

Abstract

Numerical simulation of prosthetic heart valves is a challenge to current research due to the complex geometry of the valve structure and the unsteady nature of the fluid motions. This thesis proposed an unstructured finite volume method for heart valve simulations. The Navier-Stokes equations are discretized on a general tetrahedral mesh using a finite volume scheme. With this scheme, the mesh can be automatically generated with any commercial software. Using a moving grid scheme, unsteady now of the MHV can be dynamically simulated. The simulation of the 3-D unsteady blood flow field in the mono-leaflet heart valve captured prominent features of the dynamic three-dimensional flow around the tilting disc MHV, including two jet-like streams and distinct spiral vortices, which were also observed in earlier experiments. A comparison between steady and unsteady flow solutions reveals the fact that unsteady flow in the mono-leaflet MHV contains much stronger vortices than a steady flow in the same geometry. These results point to the importance of moving-boundary unsteady flow simulations.A comprehensive dynamic unstructured moving grid finite volume algorithm, which relates fluid pressure on a MHV to the leaflet motion, is used in 3-D unsteady flow in the heart valve simulation. The solid motion of structural boundaries can be simulated both passively and actively by the scheme, in which the speed of occluder movement can be obtained from the solution. These unstructured moving grid finite volume methodologies are suitable to leaflet type MHV simulations, especially to multiple leaflet MHV simulations.The current study presents an unstructured, multi-block, moving grid finite volume method for coupled leaflet and fluid field simulations. In order to simulate the occluder motion, which is driven by the time varying pressure field, a multiple block solution procedure is implemented. With which, the flow domain is divided into blocks: one moves with the moving boundaries, while others remain stationary. This way, the grid only needs to be generated once and no grid stretching is required, thus ensuring solution accuracy and efficiency.This study is the first step in an effort to provide computational tools that can be used in the rational design of next-generation MHVs. Such an engineering tool can significantly reduce the cost and cycle time of the development process, and has the potential of becoming the enabling technology for making the MHV a true engineering device rather than an intuitive device. The 3-D time-dependent CFD model was found to give a reasonable representation of the dominant flow patterns downstream of the tilting disc heart valve, and may have the potential to be an extremely useful tool to analyze the different designs of future bileaflet heart valves.